Gene variant tied to diabetes in Greenlanders

Rare allele accounts for roughly 10 percent of type 2 cases in the population

A rare gene variant linked to a high risk of developing type 2 diabetes has been discovered in people in Greenland. Some researchers have thought that rare genetic tweaks were unlikely to cause common diseases such as type 2 diabetes, a chronic, life-threatening disease that’s on the upswing in the United States and elsewhere.

Greenlanders who carry two copies of the newly discovered variant face more than 10 times the risk of getting type 2 diabetes than people without the variant. The unusually strong effect was found by studying about 5 percent of Greenland’s small population. The finding emphasizes the need for specialized studies to uncover genetic contributions to common diseases, Torben Hansen of the University of Copenhagen and colleagues say June 18 in Nature.

The variant in a gene called TBC1D4 causes a shorter form of the gene’s protein to be made in skeletal muscles, the researchers report. As a result, muscles can’t import as much of the sugar glucose as normal. That causes a higher than normal spike in blood sugar after a meal in people with two copies of the variant.

About 17 percent of Greenland’s population carries at least one copy of the variant, the study showed. Those with one copy have slightly higher glucose levels after a meal, too, but it is the 3.8 percent of Greenlanders with two copies most at risk of getting diabetes, the researchers found. Of those people, more than 60 percent have type 2 diabetes by the time they are 40 to 60 years old. After age 60, 80 percent have the disease. The variant could explain about 10 percent of Greenland’s diabetes cases.

People outside of Greenland may carry the variant, but it is probably rare in other populations.